chore: disable TLS session tickets

Session tickets weaken forward secrecy; disable them to prevent
past sessions from being decrypted if the ticket key is compromised.

conf.d/10-defaults.conf.template

@@ -2,6 +2,7 @@ http2 on;
 ssl_protocols TLSv1.2 TLSv1.3;
 ssl_session_cache shared:SSL:10m;
 ssl_session_timeout 10m;
+ssl_session_tickets off;
 
 server {
     listen 80 default_server;